1. Field of the Invention
The present invention relates to a nonvolatile memory device, and more particularly to the configuration of a circuit which drives a current to be supplied when data is written.
2. Description of the Background Art
In recent years, nonvolatile memory devices capable of storing data in a nonvolatile manner have been mainly employed. An example thereof includes a flash memory which can be highly integrated. “A 10 ns Read and Write Non-Volatile Memory Array Using a Magnetic Tunnel Junction and FET Switch in each Cell”, 2000 IEEE ISSCC Digest of Technical Papers, TA7.2 discloses an MRAM (Magnetic Random Access Memory) device which performs nonvolatile data storage using a thin film magnetic element as a nonvolatile memory device of new generation. In addition, “Forefront of Non-Volatile Memory/The Future in Intel's Mind: From Flash Memory to OUM,” Nikkei Microdevices, March, 2002, discloses an OUM (R) (Ovonic Unified Memories) device which performs data storage using a material called a thin film calcogenide.
Generally, in the case where data storage for storing data in a memory cell employed as the memory element of one of these nonvolatile memory devices is performed, a predetermined voltage is applied to supply a current to the memory cell, thereby performing data write.
For example, in the case of an MRAM device, a predetermined data write current is generally supplied to a memory cell to thereby apply a magnetic field thereto in order to store data in accordance with a magnetic direction. Therefore, it is necessary to supply a desired data write current to a write target memory cell when data is written to the memory cell.
However, as the area of a memory array increases along with demand for mass capacity, the lengths of wirings such as a power supply wiring used for supplying the data write current and the like tend to be long.
Along with this, the resistances of the wirings such as the power supply wiring increase, with the result that a voltage level supplied from the power supply wiring often lowers by voltage drop based on the wiring resistances and the like.
As a result, the conventional technique has disadvantages in that the amount of the data write current is smaller than a desired amount and data write operation delays.